That is a good read... I sometimes go pretty fast on rappel, and I've heated up my ATC and my rap biner quite a bit, but I've never melted anything. However, my ATC can get hot enough that I'm psyched to have gloves on. I'd be interested in the data from that same test with a steel belay device...

Like many of the articles on BD's site, this one is deceiving. Okay, so the belay device wont melt a sling, but whatever, I don't tie into the belay device with a sling. The more important question is can belay devices get hot enough to melt a rope and put your life in danger? The answer is YES, despite what this BD guy is trying to imply. Just ask any experienced caver. Cavers pretty much always use huge rappel racks on long rappels because they know that any other device will overheat and melt the rope. BD's own evidence proves it. In that article BD said that in one 175-foot test rap, they were able to get the device up to 130c. Keep in mind that was only 175 feet and the weight was not free hanging which does made a difference. So if 175 feet can produce 130c, how much do you think 300' free hanging could produce? Better yet, how much could the 1,000' - 3,000' feet of rope cavers often rap down could produce? Keep in mind, in 175 feet they reached 79% of the temperature required to cause strength loss in nylon. So yes, if you are doing a rap longer than 50m, you do need to be careful or else you could critically weaken the rope from the heat. Do not read this article and think you can rap at maximum speed down any rope and never put yourself in danger of melting the rope.

Also, I dont know where they got that info about the skin burning at 212f, but here some info from John Hopkins University:

I use rappel racks to moderate the amount of friction I am applying relative to the weight of the rope. I have never come close to overheating the rack but I have only done up to 1200 feet.

Well yes, they have multiple advantages. But, my point is that cavers dont rap 1/4th a mile down on an ATC for a reason, they mostly use rap racks. I learned this when I was about to do my first 1200' rap a long time ago and I asked around on a caving forum for advice. Every reply warned me not to use anything except a large rap rack. Now, it is possible maybe a huge figure eight and some water would work, but if you try to rap a thousand feet on an ATC, expect some issues.

As far as this "myth" goes, it is not a myth. Feel free to cruise over to a caving forum and post something up along the lines of "hey guys, I am looking to do that 1250' rap down into the Cave of Swallows in Mexico and I am wondering if it is safe to use an ATC." Try it, and post up the link. It will be a shark feeding frenzy.

Also, Petzl says not to use the GriGri for raps longer than 50m for the exact same reason. They warn that raps longer than that can produce enough heat to damage the rope.

I get what you're saying but that's why it was done in relation to climbers, not cavers. Never did they mention you could do long, free rappels and be fine. In reality, I think it was totally fine. They're not being misleading by doing this in the slightest.

We did a not-dissimilar project on heating and cooling in belay devices (for abseiling) and the first thing to know is that using an IR thermometer means you are not actually measuring the temperature of the device, merely how good it is at radiating (emitting)heat in the IR spectrum. You have to make a black body radiation calibration table to get the true temperature. A stainless device for example reads about half the temperature that it really is.

I wish there were more scientific style studies with climbing related stuff. It's easy to come across things that go "so and so said they did this and that and everything was fine", and not so much studies with methods and data.

I wish there were more scientific style studies with climbing related stuff. It's easy to come across things that go "so and so said they did this and that and everything was fine", and not so much studies with methods and data.

The best resource we have in my opinion is, "accidents of north america" which is printed annually and gives first hand accounts and analysis of situations. This gives you a good idea of the risks involved and how people fared during their crisis.

Even with a rappel rack, you can heat ropes beyond the melting point if you go down too quickly. There are multiple examples of long drop deaths where the rappeller was found at the bottom of the wall with globs of melted nylon on the rack.

Heated belay devices can also "glaze" or melt the sheath of your ropes fairly easily. I do a fair bit of ascending/descending fixed lines for work and we end up replacing our lines often due to rapping with heavy loads (usually on a GriGri) too quickly. I'll see if I can get a picture up of our latest retired rope.

Even with a rappel rack, you can heat ropes beyond the melting point if you go down too quickly. There are multiple examples of long drop deaths where the rappeller was found at the bottom of the wall with globs of melted nylon on the rack.

That would be expected on a long drop if the rapper long control of the descent. It certainly doesn't prove that excessive heat and rope melting CAUSED the accident. Heck, several years ago, a sport rappeller tried to rap ElCap in one humongous drop. He lost control way up there and raced down the line to the bottom. When they found him, his torso was sawn nearly in half by the rope. No one suggested that was the cause of the accident.

Taylor - I think my point that "slow is cool enough" is more relevant to safety than your "how hot COULD it get?" inquiry. The answer to the latter of course is, "Well, how fast can you go?". And I think we all know where that leads.

That would be expected on a long drop if the rapper long control of the descent. It certainly doesn't prove that excessive heat and rope melting CAUSED the accident. Heck, several years ago, a sport rappeller tried to rap ElCap in one humongous drop. He lost control way up there and raced down the line to the bottom. When they found him, his torso was sawn nearly in half by the rope. No one suggested that was the cause of the accident. Taylor - I think my point that "slow is cool enough" is more relevant to safety than your "how hot COULD it get?" inquiry. The answer to the latter of course is, "Well, how fast can you go?". And I think we all know where that leads.

Taylor - I think my point that "slow is cool enough" is more relevant to safety than your "how hot COULD it get?" inquiry. The answer to the latter of course is, "Well, how fast can you go?". And I think we all know where that leads.

You're right Mike, I'm simply curious. Your answer is the most relevant and simple.

Still, I think it would be good to have some data on double strand rappels. I don't know about the rest of you, but I only very rarely do single strand rappels. It seems to me that double strands = more surface area on the belay device = more friction = potential for higher temps. Of course, more friction also = slower speeds. That's why I was interested in a "worse case scenario" rappel on two strands.

You're right Mike, I'm simply curious. Your answer is the most relevant and simple. Still, I think it would be good to have some data on double strand rappels. I don't know about the rest of you, but I only very rarely do single strand rappels. It seems to me that double strands = more surface area on the belay device = more friction = potential for higher temps. Of course, more friction also = slower speeds. That's why I was interested in a "worse case scenario" rappel on two strands.

Most of the resistance through the belay device is created inside the rope and with two-rope raps the plate runs considerably cooler.